Multipotential stem cells, which can differentiate to granulocytes, monocytes (macrophages), red blood cells, platelets, lymphocytes, exist in the bone marrow of higher animals such as human and mouse. The stem cells differentiate to precursory cells and the cells differentiate to the above blood cells. On the differentiation to these blood cells, several specific growth factors have been known to function to each blood cell's differentiation. For example, Interleukin-3 functions to the multipotential stem cells to induce the differentiation thereof to precursory granulocytes, and the granulocyte growth factors such as granulocyte-colony stimulating factor (G-CSF, etc.) function to the precursory cells to induce the differentiation thereof and to mature into granulocytes. With respect to the platelets, precursory cells such as megakaryocytes and platelet growth factor (MK-CSF) participate in the platelets. However, the details thereof have not been clarified.
Of various platelets which are considered to have maturation function, platelets have a significant role to maintain the health independently or in cooperation with other blood cells. Therefore, when the differentiation to platelets is inhibited, some diseases caused by reduction of platelet numbers appear.
Examples of such diseases include symptomatic thrombocytopenia, idiophatic thrombocytopenia and the like caused by medical agents (an anticancer agent, etc.), radiation, blood diseases, etc., and more specific symptoms thereof include bleeding, coagulation defect and the like.
Conventionally, as the treating method for such various thrombocytopenia, only platelets transfusion which is complicated and expensive has been used. Thus, there was no agent for the prevention and treatment of such symptoms.
The compounds of the present invention are disclosed in Japanese Patent Publication No. 62-27079 filed by the applicant as having an excellent adjuvant activity and/or preventing and treating effects on infection by microorganisms. However, it has been unknown that the compounds of the formula (I) are effective for the prevention and treatment of thrombocytopenia.